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Old 26-12-2011, 12:24   #91
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Re: Differences Between Ground, Apparent, and True Wind Direction

Quote:
Originally Posted by noelex 77 View Post
Do you guess true, apparant or ground wind
Apparently I guess true wind as I try to avoid the ground at all costs. Nonetheless, its true that if the wind is always at your back the sailing is more comfortable. That would be back-wind; not to be confused with breaking wind, which one hopes to be upwind from. The wayward wind was a song from the 1950 or 60's but I still enjoy hearing it occasionally. If this is getting long-winded...here's another thought
May the road rise to meet you,
May the wind be always at your back,
May the sun shine warm upon your face,
The rains fall soft upon your fields and,
Until we meet again,
May God hold you in the palm of His hand.
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Old 26-12-2011, 14:20   #92
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I think Dave perry debunking of lee bowing is nonsense. In my racing it's clearly understood that if you re racing towards a fixed windward mark and with a right angle current the quickest way to the mark is to put the current under the lee bow. Firstly you get pushed up towards the mark this allows to free off and hence travel faster. Equally when the tack comes to lay the mark. The current will be behind the boat. I race at times on a big river, lee bowing is very evident. Lee Bowing has no effect if the destination is water referenced. Think about it both boats start off at one side of the river to race to a mark directly to windward, ( say mark at 90) fixed to the bed of the river. The current runs from left to right. Both boats can sail equally hard to the wind. The one that keeps the current on the port side will have a shorter distance to round the mark. That's my understanding of the term.

As to the true Wind debate. Mariners for years could not compute true Wind. What they used ie boat speed sufficed most of the time so they used the term. With the arrival of gps it is possible to compute "true" ie ground wind. What should have changed was to drop the term true wind as its calculated using stw. Maybe this should have been renamed. "real wind" or something.

True wind has little use to most cruisers other then in an attempt to relate to what's really out there, most cruisers are using "true" wind to actually judge ground wind. The reason why others have never heard the term ground wind is that of course it was a solution to get instrument companies out of a hole.

Dave.
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Old 26-12-2011, 14:48   #93
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Re: Differences Between Ground, Apparent, and True Wind Direction

It looks like it gets more significant when the wind speed is low and the tide current is strong. You could get the situation where you lay the mark on one tack aided by current. The committe boats usually set the course while at anchor and move if it's not square. We come head to wind to see where it's coming from and its always favorable on the tack toward the current. When you're cruising around and you need to clear a reef that is a few hours away, you would take advantage of a lifting current and check your situation regularly. Often the current is an eddy and what's lifting you now will turn tail later.
The other item of interest is the wind rose or polar speed plot. You can use it to find the optimum course for VMG, but how do you ususally plot it? True wind, or do you calculate set and drift and compensate.
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